php -m | grep intl
Download php5-intl_5.3.10-1ubuntu3_i386.deb
extract
Copy intl.so to ~/.phpenv/versions/5.3.28/lib/php/extensions/no-debug-non-zts-20090626/
Add this line to the end of ~/.phpenv/versions/5.3.28/etc/php.ini
extension=intl.so